I was very stunned, then I read the paper, thought about it, and am skeptical of the claim that the bacteria uses As-DNA as its genetic material (it may contain As-DNA, but these would likely be nonfunctional). For my (very longwinded) thoughts on the paper, see my post on the biology board (https://www.physicsforums.com/showthread.php?p=3016806#post3016806).Are you stunned?
It still uses some phosphorus, so it hasn't swapped ALL of it out for arsenic, but still, it's pretty freaking cool.
Despite my skepticism, I still think the paper is very neat and exciting. Who knows what other undiscovered biochemistires are out these in other extreme environments.